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Commit 278b2083 authored by nikolay@redhat.com's avatar nikolay@redhat.com Committed by David S. Miller
Browse files

bonding: initial RCU conversion 



This patch does the initial bonding conversion to RCU. After it the
following modes are protected by RCU alone: roundrobin, active-backup,
broadcast and xor. Modes ALB/TLB and 3ad still acquire bond->lock for
reading, and will be dealt with later. curr_active_slave needs to be
dereferenced via rcu in the converted modes because the only thing
protecting the slave after this patch is rcu_read_lock, so we need the
proper barrier for weakly ordered archs and to make sure we don't have
stale pointer. It's not tagged with __rcu yet because there's still work
to be done to remove the curr_slave_lock, so sparse will complain when
rcu_assign_pointer and rcu_dereference are used, but the alternative to use
rcu_dereference_protected would've created much bigger code churn which is
more difficult to test and review. That will be converted in time.

1. Active-backup mode
 1.1 Perf recording while doing iperf -P 4
  - old bonding: iperf spent 0.55% in bonding, system spent 0.29% CPU
                 in bonding
  - new bonding: iperf spent 0.29% in bonding, system spent 0.15% CPU
                 in bonding
 1.2. Bandwidth measurements
  - old bonding: 16.1 gbps consistently
  - new bonding: 17.5 gbps consistently

2. Round-robin mode
 2.1 Perf recording while doing iperf -P 4
  - old bonding: iperf spent 0.51% in bonding, system spent 0.24% CPU
                 in bonding
  - new bonding: iperf spent 0.16% in bonding, system spent 0.11% CPU
                 in bonding
 2.2 Bandwidth measurements
  - old bonding: 8 gbps (variable due to packet reorderings)
  - new bonding: 10 gbps (variable due to packet reorderings)

Of course the latency has improved in all converted modes, and moreover
while
doing enslave/release (since it doesn't affect tx anymore).

Also I've stress tested all modes doing enslave/release in a loop while
transmitting traffic.

Signed-off-by: default avatarNikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 15077228

drivers/net/bonding/bond_3ad.c

+2 −0
Original line number Diff line number Diff line
@@ -2426,6 +2426,7 @@ int bond_3ad_xmit_xor(struct sk_buff *skb, struct net_device *dev) 
	struct ad_info ad_info;

	int res = 1;



	read_lock(&bond->lock);

	if (__bond_3ad_get_active_agg_info(bond, &ad_info)) {

		pr_debug("%s: Error: __bond_3ad_get_active_agg_info failed\n",

			 dev->name);
@@ -2475,6 +2476,7 @@ int bond_3ad_xmit_xor(struct sk_buff *skb, struct net_device *dev) 
	}



out:

	read_unlock(&bond->lock);

	if (res) {

		/* no suitable interface, frame not sent */

		kfree_skb(skb);

drivers/net/bonding/bond_alb.c

+4 −2
Original line number Diff line number Diff line
@@ -1337,6 +1337,7 @@ int bond_alb_xmit(struct sk_buff *skb, struct net_device *bond_dev) 


	/* make sure that the curr_active_slave do not change during tx

	 */

	read_lock(&bond->lock);

	read_lock(&bond->curr_slave_lock);



	switch (ntohs(skb->protocol)) {
@@ -1441,11 +1442,12 @@ int bond_alb_xmit(struct sk_buff *skb, struct net_device *bond_dev) 
	}



	read_unlock(&bond->curr_slave_lock);



	read_unlock(&bond->lock);

	if (res) {

		/* no suitable interface, frame not sent */

		kfree_skb(skb);

	}



	return NETDEV_TX_OK;

}
@@ -1663,7 +1665,7 @@ void bond_alb_handle_active_change(struct bonding *bond, struct slave *new_slave 
	}



	swap_slave = bond->curr_active_slave;

	bond->curr_active_slave = new_slave;

	rcu_assign_pointer(bond->curr_active_slave, new_slave);



	if (!new_slave || list_empty(&bond->slave_list))

		return;

drivers/net/bonding/bond_main.c

+15 −15
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ 
#include <net/net_namespace.h>

#include <net/netns/generic.h>

#include <net/pkt_sched.h>

#include <linux/rculist.h>

#include "bonding.h"

#include "bond_3ad.h"

#include "bond_alb.h"
@@ -1037,7 +1038,7 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active) 
		if (new_active)

			bond_set_slave_active_flags(new_active);

	} else {

		bond->curr_active_slave = new_active;

		rcu_assign_pointer(bond->curr_active_slave, new_active);

	}



	if (bond->params.mode == BOND_MODE_ACTIVEBACKUP) {
@@ -1127,7 +1128,7 @@ void bond_select_active_slave(struct bonding *bond) 
 */

static void bond_attach_slave(struct bonding *bond, struct slave *new_slave)

{

	list_add_tail(&new_slave->list, &bond->slave_list);

	list_add_tail_rcu(&new_slave->list, &bond->slave_list);

	bond->slave_cnt++;

}
@@ -1143,7 +1144,7 @@ static void bond_attach_slave(struct bonding *bond, struct slave *new_slave) 
 */

static void bond_detach_slave(struct bonding *bond, struct slave *slave)

{

	list_del(&slave->list);

	list_del_rcu(&slave->list);

	bond->slave_cnt--;

}
@@ -1751,7 +1752,7 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev) 
		 * so we can change it without calling change_active_interface()

		 */

		if (!bond->curr_active_slave && new_slave->link == BOND_LINK_UP)

			bond->curr_active_slave = new_slave;

			rcu_assign_pointer(bond->curr_active_slave, new_slave);



		break;

	} /* switch(bond_mode) */
@@ -1951,7 +1952,7 @@ static int __bond_release_one(struct net_device *bond_dev, 
	}



	if (all) {

		bond->curr_active_slave = NULL;

		rcu_assign_pointer(bond->curr_active_slave, NULL);

	} else if (oldcurrent == slave) {

		/*

		 * Note that we hold RTNL over this sequence, so there
@@ -1983,6 +1984,7 @@ static int __bond_release_one(struct net_device *bond_dev, 


	write_unlock_bh(&bond->lock);

	unblock_netpoll_tx();

	synchronize_rcu();



	if (list_empty(&bond->slave_list)) {

		call_netdevice_notifiers(NETDEV_CHANGEADDR, bond->dev);
@@ -3811,7 +3813,7 @@ void bond_xmit_slave_id(struct bonding *bond, struct sk_buff *skb, int slave_id) 
	int i = slave_id;



	/* Here we start from the slave with slave_id */

	bond_for_each_slave(bond, slave) {

	bond_for_each_slave_rcu(bond, slave) {

		if (--i < 0) {

			if (slave_can_tx(slave)) {

				bond_dev_queue_xmit(bond, skb, slave->dev);
@@ -3822,7 +3824,7 @@ void bond_xmit_slave_id(struct bonding *bond, struct sk_buff *skb, int slave_id) 


	/* Here we start from the first slave up to slave_id */

	i = slave_id;

	bond_for_each_slave(bond, slave) {

	bond_for_each_slave_rcu(bond, slave) {

		if (--i < 0)

			break;

		if (slave_can_tx(slave)) {
@@ -3848,7 +3850,7 @@ static int bond_xmit_roundrobin(struct sk_buff *skb, struct net_device *bond_dev 
	 * will send all of this type of traffic.

	 */

	if (iph->protocol == IPPROTO_IGMP && skb->protocol == htons(ETH_P_IP)) {

		slave = bond->curr_active_slave;

		slave = rcu_dereference(bond->curr_active_slave);

		if (slave && slave_can_tx(slave))

			bond_dev_queue_xmit(bond, skb, slave->dev);

		else
@@ -3870,7 +3872,7 @@ static int bond_xmit_activebackup(struct sk_buff *skb, struct net_device *bond_d 
	struct bonding *bond = netdev_priv(bond_dev);

	struct slave *slave;



	slave = bond->curr_active_slave;

	slave = rcu_dereference(bond->curr_active_slave);

	if (slave)

		bond_dev_queue_xmit(bond, skb, slave->dev);

	else
@@ -3900,7 +3902,7 @@ static int bond_xmit_broadcast(struct sk_buff *skb, struct net_device *bond_dev) 
	struct bonding *bond = netdev_priv(bond_dev);

	struct slave *slave = NULL;



	bond_for_each_slave(bond, slave) {

	bond_for_each_slave_rcu(bond, slave) {

		if (bond_is_last_slave(bond, slave))

			break;

		if (IS_UP(slave->dev) && slave->link == BOND_LINK_UP) {
@@ -3955,7 +3957,7 @@ static inline int bond_slave_override(struct bonding *bond, 
		return 1;



	/* Find out if any slaves have the same mapping as this skb. */

	bond_for_each_slave(bond, check_slave) {

	bond_for_each_slave_rcu(bond, check_slave) {

		if (check_slave->queue_id == skb->queue_mapping) {

			slave = check_slave;

			break;
@@ -4040,14 +4042,12 @@ static netdev_tx_t bond_start_xmit(struct sk_buff *skb, struct net_device *dev) 
	if (is_netpoll_tx_blocked(dev))

		return NETDEV_TX_BUSY;



	read_lock(&bond->lock);



	rcu_read_lock();

	if (!list_empty(&bond->slave_list))

		ret = __bond_start_xmit(skb, dev);

	else

		kfree_skb(skb);



	read_unlock(&bond->lock);

	rcu_read_unlock();



	return ret;

}

drivers/net/bonding/bond_sysfs.c

+7 −12
Original line number Diff line number Diff line
@@ -1243,16 +1243,16 @@ static ssize_t bonding_show_active_slave(struct device *d, 
					 struct device_attribute *attr,

					 char *buf)

{

	struct slave *curr;

	struct bonding *bond = to_bond(d);

	struct slave *curr;

	int count = 0;



	read_lock(&bond->curr_slave_lock);

	curr = bond->curr_active_slave;

	read_unlock(&bond->curr_slave_lock);



	rcu_read_lock();

	curr = rcu_dereference(bond->curr_active_slave);

	if (USES_PRIMARY(bond->params.mode) && curr)

		count = sprintf(buf, "%s\n", curr->dev->name);

	rcu_read_unlock();



	return count;

}
@@ -1284,7 +1284,7 @@ static ssize_t bonding_store_active_slave(struct device *d, 
	if (!strlen(ifname) || buf[0] == '\n') {

		pr_info("%s: Clearing current active slave.\n",

			bond->dev->name);

		bond->curr_active_slave = NULL;

		rcu_assign_pointer(bond->curr_active_slave, NULL);

		bond_select_active_slave(bond);

		goto out;

	}
@@ -1347,14 +1347,9 @@ static ssize_t bonding_show_mii_status(struct device *d, 
				       struct device_attribute *attr,

				       char *buf)

{

	struct slave *curr;

	struct bonding *bond = to_bond(d);



	read_lock(&bond->curr_slave_lock);

	curr = bond->curr_active_slave;

	read_unlock(&bond->curr_slave_lock);



	return sprintf(buf, "%s\n", curr ? "up" : "down");

	return sprintf(buf, "%s\n", bond->curr_active_slave ? "up" : "down");

}

static DEVICE_ATTR(mii_status, S_IRUGO, bonding_show_mii_status, NULL);

drivers/net/bonding/bonding.h

+4 −0
Original line number Diff line number Diff line
@@ -116,6 +116,10 @@ 
#define bond_for_each_slave(bond, pos) \

	list_for_each_entry(pos, &(bond)->slave_list, list)



/* Caller must have rcu_read_lock */

#define bond_for_each_slave_rcu(bond, pos) \

	list_for_each_entry_rcu(pos, &(bond)->slave_list, list)



/**

 * bond_for_each_slave_reverse - iterate in reverse from a given position

 * @bond:	the bond holding this list